The present invention relates to archery bows, and more particularly to bowstring weights commonly identified as string nocks or speed nocks.
Conventional archery bows, and in particular compound archery bows, include a bowstring and a set of cables that transfer energy from the limbs and cams or pulleys of the bow to the bowstring, and thus to an arrow shot from the bow. To reduce vibration, and to further increase the energy imparted to the arrow by the bow, optional weights, such as string nocks or speed nocks (both referred to as speed nocks herein) are strategically positioned on the bowstring, typically at one or more vibration nodes along the bowstring.
Typically, the speed nocks are placed on either or both of the upper and lower portions of the bowstring, near to the cams on a double cam bow, or near the cam and near the pulley on a single cam bow. The size of the speed nock and its location on the bowstring typically increase the energy imparted to the arrow by the bow, and accordingly increase arrow speed. The weight and location of speed nocks are usually unique to the type of bow and related equipment, such as arrows or accessories attached to the bow, and normally differ for the upper and/or lower portions of the bowstring as well. Any changes made to the equipment may require modification in the location of the speed nocks and possibly the weight and or size of the speed nocks. Usually, the optimum weights and locations are achieved by trial and error testing, in which an arrow is shot through a speed-measuring chronograph repeatedly. The placement and/or weights of the speed nocks are adjusted until the fastest arrow speed is identified.
Conventional speed nocks are split metal “U” shaped devices, usually having a brass outer portion and an inner portion that is a softer material that engages a serving of the bowstring or the bowstring itself. The “U” shaped device is placed around the bowstring, and the “U” is crimped so that it fully encircles the bowstring, and is held in a specific location.
Achieving the desired location, as noted above, is an iterative process with the “U” shaped speed nocks. This process includes initially crimping at least one speed nock to each end of the bowstring near the cams, and shooting multiple arrows, while measuring the arrow speed of each shot with a chronograph. The nocks are un-crimped, moved incrementally along the bowstring, and then re-crimped. The arrows subsequently are shot again and the arrow speed is measured. These steps are repeated until the “sweet spot” is located where the arrow speed peaks. If additional nocks are desired, the process starts anew.
For safety reasons, many archers secure the “U” shaped nocks by heat shrinking tubing over the nocks to prevent them from, possibly disengaging the string and causing injury. Application of the heat shrink tubing usually requires unstringing and restringing the bow after the “sweet spots” are determined.
The inner portion of most “U” shaped speed nocks is an elastomer that, as mentioned above, engages the bowstring or serving, and alleviates damage to the bowstring. While the elastomer reduces some wear on the string, where multiple crimping and uncrimping steps in the trial and error process are performed, the elastomer or metal part can wear on the individual fibers of the strands of the bowstring, prematurely shortening the life of the bowstring.
There are other speed nocks in the market that have a different structure. For example, another speed nock, commercially available from T.R.U. Ball® under the Speed Nok name, includes aluminum parts that define grooves adapted to receive the bowstring. The parts are secured around the bowstring by clamping them together with integral screws. The bowstring remains trapped within the parts.
Another example of a speed nock is a segment of rubber or similar elastomeric tubing material that encircles the bowstring. The tubing can be in the form either of individual segments or as segments that are defined by partial cuts in the tubing. In either form, the number of segments needed are estimated and then threaded on the bowstring before stringing the bow. The segments are moved up or down the exterior of the bowstring until the optimum locations are determined. If the estimated number of segments is inadequate, the bow must be un-strung. Additional segments must be threaded on the bowstring, and the bow re-strung. The segments remain in place at the selected locations by the gripping properties of the elastomeric material.
Although the above conventional bowstring speed nocks may achieve the desired objective, there remains room for improvement.